The sound from one side (left or right) of the headphones is very low.

The troubleshooting steps on this article have been written to work with all types of Sony® headphones. Because of this, some steps are only spelled out in general terms. The reason for this is that the process to perform that particular step is different depending on the headphones you have. For information specific to any particular model on how to complete any of the steps in this solution, refer to the operating instructions supplied with your product.
Manuals are posted on your model support page.